Process for reducing the NOx content in waste gases

Abstract

In a process for reducing the NO x content of waste gases by a catalytic reduction of the NO x gases using a washable catalyst, a solution is to be provided, with which, while retaining the advantages of the procedure known from the German Offenlegungsschrift No. 3,107,117, this danger is avoided and which is suitable for use with a large range of waste gases, that is, which in particular is not restricted to nitric acid plants. This is accomplished owing to the fact that the reduction is carried out using unsaturated hydrocarbons at a temperature equal to or less than 180° C.

I claim: 
     
       1. In a process for reducing the NO x  content of waste gases from power plants operated with fossil fuel by means of a catalytic reduction of the NO x  gases using a washable catalyst, wherein the reduction is carried out using a reducing effective amount of unsaturated hydrocarbons at a temperature equal to or less than 180° C., the improvement which comprises obtaining all of the unsaturated hydrocarbons used for the reduction directly from the waste gas stream. 
     
     
       2. The process of claim 1 wherein hydrocarbons with double bonds or triple bonds are used as hydrocarbons. 
     
     
       3. The process of claim 2 wherein mixtures of hydrocarbons with double bonds and triple bonds are used as hydrocarbons. 
     
     
       4. The process of claim 1 wherein the waste gas stream is passed through a bed of catalyst granulates in order to reduce it catalytically. 
     
     
       5. The process of claim 1 where in the waste gas stream is passed between catalyst plates. 
     
     
       6. The process of claim 1 wherein the waste gas is intimately mixed with the hydrocarbons before it enters the catalyst.